The present invention relates to an information recording method utilizing light, and more particularly to a multiple frequency recording method which utilizes hole burning.
Various researches have hitherto been made on the multiple-frequency optical recording which utilizes the hole burning phenomenon, and they are described in, for example, "Angewandte Chemie" International Edition, English 23, (1984) pp. 113-140. With any of the prior-art methods, the multiplicity in the direction of wavelengths is very high. Since, however, a medium of great light absorption coefficient is not available, the unit recording area of the prior-art method is large, and the overall recording density thereof does not considerably differ from that of a conventional optical recording method.
In the prior art, light absorption centers such as dye molecules or color centers cannot have their density made very high lest the interactions among the centers should intensify to change the property of a light absorption band. In order to attain the practical signal-to-noise ratio of read signals, accordingly, a light projection extent (unit storage region) on a recording medium must be enlarged. Usually, the area of the unit storage region is about 100 times that of an optical disk, so that even if recording at a multiplicity of 1000 is possible, the actual storage capacity per unit area becomes only 10 times.